Sale #1:

http://www.tf2outpost.com/trade/25922103

Quick-sold for 22 keys + minor items/metal ~22 keys

Seller:

http://backpack.tf/profiles/76561198072744029?time=1431414000 (May 12th)

http://backpack.tf/profiles/76561198072744029?time=1431586800 (May 14th)

Buyer:

http://backpack.tf/profiles/76561198058238959?time=1431500400 (May 13th)

http://backpack.tf/profiles/76561198058238959?time=1431586800 (May 14th)

Sale #2:

http://www.tf2outpost.com/trade/25882620

Hard to say what this sold for, next owner is asking 29 keys http://www.tf2outpost.com/trade/26005285

Was asking 33 keys.

Sale #3:

http://www.tf2outpost.com/trade/25864345

Sold for an Australium Scattergun (35)

http://backpack.tf/profiles/76561198122359753?time=1430636400 (May 3rd)

http://backpack.tf/profiles/76561198122359753?time=1430809200 (May 5th)

35 * 0.9 = 32 keys - the seller's B/O

Sellers:

http://www.tf2outpost.com/trade/26005285 29 keys, offered Blizz Beanie + 15 keys

http://www.tf2outpost.com/trade/25816140 30 keys, offered DBD Ushanka + KaW Pirate Bandana

22 keys is probably low here. Low-end is from the seller at 30 keys for a month.